1. Field of the Invention
The present invention relates to the method and apparatus for fabricating a fiber reinforced plastic bundle or rod and more particularly to such a bundle or rod having a substantially smooth surface and improved physical properties.
2. Description of the Prior Art
Meek U.S. Pat. No. 2,684,318 discloses a method for fabricating plastic rods reinforced with glass fiber by the pultrusion method whereby a plurality of strands of glass fiber are collected together in a bundle, the strands and bundle passed through a bath of liquid resin, then through a forming die from which it emerges and passes through an elongated heating chamber which serves to substantially harden the resin. The process is one of continuous movement of the bundle and the cured rod is cut into lengths as needed. Upon emerging from the forming die, the bundle is exposed to the atmosphere, there being no force applied to the exterior of the bundle to hold it to size and shape. As a consequence, the natural resiliency of the fibers causes them to project from the bundle surface and further for the bundle itself to expand slightly in cross section. While in the heating chamber, heat energy is conveyed to the bundle by convection until the plastic is cured to hardened condition. The cured rod while solid has a rough, textured surface which must be ground smooth if the rod is to be used for such purposes as fishing poles, golf shafts, strain cables and the like.
Such a bundle if wetted with polyester resin has the property that if drawn through a sizing die which is itself heated, the resin tends to stick to the die surface and further to cure in such a manner that upon emergence from the die the surface is rough and of flaky appearance. In order to overcome the problem in the form of the rough surface, various different resin systems and release agents have been experimented with without apparent success. Further, the rod or bundle has been preheated inside the die to near gel temperature and the rod then allowed to cure outside the die, this also not being successful.
Other prior efforts to produce such fiber reinforced rods by the use of die elements are disclosed in U.S. Pat. Nos. 2,741,294, 2,816,595, 2,948,649, 3,244,784 and 2,818,606.